Verification: xxxx

Proof: xxxx

Proof should have basis, such as formula, theorem and definition. When you first make a proof, you'd better add an argument at the back, which will be clear and sufficient. For example, ∫a = b a = c ∴b=c (equivalent substitution), and ∫△ABC is a right triangle, ∴ C2 = A 2+B 2 (Pythagorean theorem).